1. Field of the Invention
This invention relates to a method of reforming gasoline to raise the octane number thereof utilizing a novel catalyst comprising a low valence titanium, vanadium and/or chromium metallic component composited with a non-oxidizing high surface area support. The low valence metallic component is present in divalent form or as a combination of the metallic state and the divalent form--preferably a chloride and/or bromide and the support is preferably a high surface area coke.
2. Description of the Prior Art
Vanadium, titanium and chromium have previously been used as a catalytic component in hydrocarbon conversion processes.
In U.S. Pat. No. 3,282,828, colloidally dispersed unsupported vanadium halides which may be in divalent form are disclosed as suitable slurry catalyst in the hydrorefining or decontaminating of petroleum crude oil and other heavy hydrocarbon fractions.
However, as taught in U.S. Pat. No. 3,282,828, the use of vanadium-containing catalyst in fixed-bed catalytic processes or fixed-fluidized bed processes has been virtually precluded due to the difficulty of maintaining such catalyst in active condition. Likewise, moving-bed processes utilizing supported vanadium also have not been satisfactory.
N. S. Koslov et al in an article published in NEFTE KHIMIYA (Petroleum Chemistry), Vol. 19, No. 3, P. 37D (1979) entitled: THE EFFECT OF CHROMIUM ON THE ACTIVITY OF PLATINUM-ALUMINA CATALYST IN DEHYDRATION AND DEHYDROCYCLIZATION REACTIONS disclosed that addition of chromium to Pt-Al.sub.2 O.sub.3 catalysts, reduced cracking side reactions and increased conversion and selectivity for n-heptane dehydrocyclization reactions. Koslov et al disclose that for the dehydrocyclization of n-heptane with their Pt-Cr-Al.sub.2 O.sub.3 catalyst, coke increases with Cr content but goes through a maximum and then decreases. At 3% Cr the coke make is less than for a Pt-Al.sub.2 O.sub.3 catalyst without Cr. The authors attribute the foregoing characteristics of chromium promoted Pt-Al.sub.2 O.sub.3 catalysts to the increased dispersion and decreased particle size of platinum observed where the Pt is promoted with Cr within a given range.
In the present invention, it has been discovered that the reforming of gasoline can be effected utilizing a vanadium, titanium or chormium-containing catalyst which possesses and retains activity in both fixed-bed and moving-bed processes. The catalyst of the present invention comprises a combination of (a) one or more of the metallic components V, Ti and Cr in their lower valent states; the metallic components can be present in the +2 valence state or in the form of both the metal and +2 valence state metal such that the "average valence" in the catalyst may vary from about +1 up to +2; and, (b) a high surface area support for the metallic component(s) which is characterized by surface area maintenance at reaction and/or activation conditions and most importantly by the property of not oxidizing the metallic components to the +3 or higher valence states over the temperature range to which said catalyst is subjected. As will be explained more fully hereafter, this excludes the use of refractory oxides, such as the Al.sub.2 O.sub.3 support of Koslov et al, which it has been found can under some conditions oxidize lower-valence salts such as metallic or divalent vanadium to higher oxidation states. A suitable support is a non-oxygen containing high surface area material such as high surface area coke.